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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.network.protocol;
import java.io.IOException;
import java.nio.channels.WritableByteChannel;
import javax.annotation.Nullable;
import com.google.common.base.Preconditions;
import io.netty.buffer.ByteBuf;
import io.netty.channel.FileRegion;
import io.netty.util.AbstractReferenceCounted;
import io.netty.util.ReferenceCountUtil;
import org.apache.spark.network.buffer.ManagedBuffer;
/**
* A wrapper message that holds two separate pieces (a header and a body).
*
* The header must be a ByteBuf, while the body can be a ByteBuf or a FileRegion.
*/
class MessageWithHeader extends AbstractReferenceCounted implements FileRegion {
@Nullable private final ManagedBuffer managedBuffer;
private final ByteBuf header;
private final int headerLength;
private final Object body;
private final long bodyLength;
private long totalBytesTransferred;
/**
* Construct a new MessageWithHeader.
*
* @param managedBuffer the {@link ManagedBuffer} that the message body came from. This needs to
* be passed in so that the buffer can be freed when this message is
* deallocated. Ownership of the caller's reference to this buffer is
* transferred to this class, so if the caller wants to continue to use the
* ManagedBuffer in other messages then they will need to call retain() on
* it before passing it to this constructor. This may be null if and only if
* `body` is a {@link FileRegion}.
* @param header the message header.
* @param body the message body. Must be either a {@link ByteBuf} or a {@link FileRegion}.
* @param bodyLength the length of the message body, in bytes.
*/
MessageWithHeader(
@Nullable ManagedBuffer managedBuffer,
ByteBuf header,
Object body,
long bodyLength) {
Preconditions.checkArgument(body instanceof ByteBuf || body instanceof FileRegion,
"Body must be a ByteBuf or a FileRegion.");
this.managedBuffer = managedBuffer;
this.header = header;
this.headerLength = header.readableBytes();
this.body = body;
this.bodyLength = bodyLength;
}
@Override
public long count() {
return headerLength + bodyLength;
}
@Override
public long position() {
return 0;
}
@Override
public long transfered() {
return totalBytesTransferred;
}
/**
* This code is more complicated than you would think because we might require multiple
* transferTo invocations in order to transfer a single MessageWithHeader to avoid busy waiting.
*
* The contract is that the caller will ensure position is properly set to the total number
* of bytes transferred so far (i.e. value returned by transfered()).
*/
@Override
public long transferTo(final WritableByteChannel target, final long position) throws IOException {
Preconditions.checkArgument(position == totalBytesTransferred, "Invalid position.");
// Bytes written for header in this call.
long writtenHeader = 0;
if (header.readableBytes() > 0) {
writtenHeader = copyByteBuf(header, target);
totalBytesTransferred += writtenHeader;
if (header.readableBytes() > 0) {
return writtenHeader;
}
}
// Bytes written for body in this call.
long writtenBody = 0;
if (body instanceof FileRegion) {
writtenBody = ((FileRegion) body).transferTo(target, totalBytesTransferred - headerLength);
} else if (body instanceof ByteBuf) {
writtenBody = copyByteBuf((ByteBuf) body, target);
}
totalBytesTransferred += writtenBody;
return writtenHeader + writtenBody;
}
@Override
protected void deallocate() {
header.release();
ReferenceCountUtil.release(body);
if (managedBuffer != null) {
managedBuffer.release();
}
}
private int copyByteBuf(ByteBuf buf, WritableByteChannel target) throws IOException {
int written = target.write(buf.nioBuffer());
buf.skipBytes(written);
return written;
}
}
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